A method for phytoremediation of heavy metal contaminated soil by combined planting of plants and its application

Abstract

The present invention relates to the field of remediation of heavy metal contaminated soil, and discloses a method and application for phytoremediation of heavy metal contaminated soil by combined planting of plants. The present invention selects shrubs and herbaceous plants with relatively fast growth rates and that can be repeatedly harvested, and adopts a plant configuration mode of "shrub + herbaceous". By utilizing the characteristics of rapid growth of shrubs and herbaceous plants, the problem of slow existing phytoremediation can be solved. According to the different root depths of shrubs and herbaceous plants, the remediation of heavy metal contaminated soil in different soil layers can be taken into account. For example, the characteristics of deep roots of shrubs such as Schefflera odorata var. variegata and Nerium oleander can be used to remediate heavy metal contaminated soil in deeper soil layers, and the characteristics of shallow roots of herbaceous plants such as Pennisetum alopecuroides and Ruellia brittoniana can be used to remediate surface contaminated soil; after planting, by slightly pruning the shrubs and appropriately pruning the herbaceous plants, a relatively good landscape effect can be formed; by regularly harvesting fast-growing shrubs and herbaceous plants such as Schefflera odorata var. variegata, Pennisetum alopecuroides and Ruellia brittoniana, the effect of repeated adsorption can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of remediation of heavy metal contaminated soil, and particularly to a method and application for phytoremediation of heavy metal contaminated soil by combined planting of plants. Background Art

[0002] With the rapid development of urbanization and industrialization, a large number of emissions such as gases, liquids, and solids containing heavy metals and other pollutants are discharged into the natural environment, resulting in heavy metal pollution of the soil. [1-3] Heavy metal elements are not easily leached with water in the soil, and are not easily decomposed naturally, but are easily absorbed and accumulated by organisms, and can even accumulate in the human body through the food chain, seriously endangering human health. [4-5] These heavy metal elements remaining in the soil, if not effectively repaired, will become "chemical time bombs", threatening the ecological environment safety at any time. Therefore, the remediation of contaminated soil is imminent, and the remediation of contaminated soil is also an important measure to ensure ecological safety.

[0003] There are mainly two ways to control soil heavy metal pollution. One is to change the existing form of heavy metals in the soil to fix them and reduce their mobility and bioavailability in the environment; the other is to remove heavy metals from the soil. At present, around these two control ways, respective chemical, physical, and biological treatment methods have been proposed. [6-8] The chemical remediation method is to put a modifier into the soil, and through the adsorption, redox, antagonism or precipitation of heavy metals, to reduce the bioavailability of heavy metals. Although chemical remediation is simple and easy to operate, it only changes the existing form of heavy metals in the soil, and the metal elements still remain in the soil, and are easy to be reactivated and endanger the ecological environment. [9-10] Physical remediation mainly uses the differences in the respective physical properties between pollutants and the environment to achieve the purpose of removing and separating pollutants from the environment. Common physical remediation methods include direct soil replacement method, electrokinetic remediation method, soil washing method, etc. However, these remediation methods often have disadvantages such as large project volume, high cost, high requirements for soil, and are not suitable for large-scale soil remediation engineering projects.

[11] Bioremediation is to use organisms to reduce and purify heavy metals in the soil or reduce the toxicity of heavy metals. This method has good effects and is easy to operate, and has received people's attention and has increasingly become a research hotspot for remediating contaminated soil.

[12] Phytoremediation is a new bioremediation technology, which has advantages that cannot be compared with physical and chemical remediation methods. Specifically, it has low treatment cost and permanent effect. The phytoremediation process is in-situ remediation, which does not require excavation, transportation, and huge treatment sites, has little disturbance to the soil environment, does not damage the soil ecological environment, and can keep the soil in a good structure and fertility state; the remediation process generally has no secondary pollution, and some metal elements can even be recycled.

[13] ; The planted plants have both landscape effects and can beautify the environment. Therefore, phytoremediation is a reliable and relatively environmentally safe technology, a true "green remediation technology".

[0004] At present, phytoremediation technology has been widely applied to the remediation of heavy metal-polluted soils in cities. For example, plants such as ramie, Sedum alfredii Hance, Viburnum odoratissimum Ker-Gawl., and Viburnum tinus L. have good remediation effects on cadmium-polluted soils. [14-16] , plants such as Pteris multifida Poir., Jasminum sambac (L.) Aiton, and Cynodon dactylon (L.) Pers. have good remediation effects on lead-polluted soils. [17-19] , Cyperus rotundus L., Sedum erythrostictum Miq., Sonchus oleraceus L., etc. have good adsorption effects on zinc. [20-22] .

[0005] Existing hyperaccumulator plants have a certain selectivity for heavy metals and generally only have the ability to hyperaccumulate one or two heavy metals. However, most of the actually polluted soils are contaminated with several heavy metals in combination. Therefore, it is difficult for a single plant to comprehensively purify various pollutants in the soil. A Chinese invention patent application with the publication number CN103962369A discloses a method for remediating heavy metal-polluted soils by using an energy plant configuration mode. This method can remediate lead-zinc polluted soils by intercropping or mixed planting of plants. However, due to the different heavy metal components in the polluted soil and the different intercropped plants, the final heavy metal accumulation amounts in the plants are also different. The inventor's investigation found that the heavy metal pollution in the urban green space soil in Foshan City mainly includes six heavy metal elements: Cu, Zn, Pb, Cd, Cr, and Ni. Therefore, it is of great practical significance to develop and design a plant configuration mode with a large accumulation amount of six heavy metal elements: Cu, Zn, Pb, Cd, Cr, and Ni.

[0006] References.

[0007] [1] Liu Peng, Hu Wenyou, Huang Biao, etc.; The impact of atmospheric deposition on the enrichment of heavy metals in soil and crops and its research progress [J]; Acta Pedologica Sinica, 2019, 56(5): 1048-1059.

[0008] [2] Fu Guowei, Control countermeasures for heavy metal pollution in soil and water in China [J]; China Environmental Science, 2012, 32(2): 373-376.

[0009] [3] Chen Yali, Weng Liping, Ma Jie, etc.; Research progress on source apportionment of soil heavy metals in China in the past decade [J]; Journal of Agro-Environment Science, 2019, 38(10): 2219-2238.

[0010] [4] Xu Guoliang, Wen Ya, Cai Shaoyan, etc.; Review of research on the impact of urban surface soil on ecological health [J]; Geographical Research, 2019, 38(12): 2941-2956.

[0011] [5] Park B Y, Lee J K, Ro H M, et al. Effects of heavy metal contamination from an abandoned mine on nematode community structure as an indicator of soil ecosystem health[J]; Applied Soil Ecology, 2011, 51: 17-24。

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[0015] [9] Zou Xueyan, Li Xiaohong, Zhao Yanbao, et al.; Research progress on the remediation of heavy metal contaminated soil by chemical passivation method[J]; Chemical Research, 2018, 29(06):14-23。

[0016]

[10] Yan Yan, Du Wenwen; Discussion on the treatment methods and research prospects of soil heavy metals[J]; Science and Technology Innovation, 2019(13):185-186。

[0017]

[11] Liu Kan, Wang Bo, Quan Junjiao, et al.; Research progress on the remediation of soil heavy metal pollution[J]; Northern Horticulture, 2012(22):189-194。

[0018]

[12] Qu Ran, Meng Wei, Li Junsheng, et al.; Phytoremediation of soil heavy metal pollution[J]; Chinese Journal of Ecology, 2008, 27(004):626-631。

[0019]

[13] Wang Que, Zhang Jinda, Chen Zhehan, Dai Yonglai; Research progress on heavy metal contaminated soil remediation technology[J]; Energy Environmental Protection, 2019,33(03):5-9。

[0020]

[14] Xiang Yaling, Lin Qufei, Hu Qiulan, Liu Xuefeng; Cadmium absorption characteristics of ramie and improvement of cadmium contaminated farmland[J]; China Fiber Crops, 1994(02):39-42。

[0021]

[15] Yu Qi, Cadmium Hyperaccumulation Characteristics and Molecular Mechanisms of Sedum alfredii Hance [D], Central China Normal University, 2020.

[0022]

[16] Du Xiao, Shen Xiaohui; Effects of Cadmium Stress on Physiological and Biochemical Indexes of Viburnum odoratissimum Ker-Gawl. and Viburnum tinus L. [J]; Chinese Journal of Ecology, 2010, 29(05): 899-904.

[0023]

[17] Xu Chenming, Bao Lining, Zhang Jin, Jiang Yu; Research on the Remediation Mechanism of Pteris vittata L. on Lead-Contaminated Soil [J], Journal of Anhui Agricultural University, 2020, 47(02): 260-266.

[0024]

[18] Zhu Lixia, Lin Yihan, Lu Luanmei, Zhang Qiong, Cai Yueqin, Lu Jun, Han Xingang; Study on the Resistance and Enrichment Characteristics of Jasminum sambac (L.) Ait. to Four Kinds of Heavy Metal-Contaminated Soils [J], Fujian Science & Technology of Tropical Crops, 2020, 45(02): 17-22.

[0025]

[19] Zhang Hao, Zhang Lingyun, Wang Ji, Cai Xiongfei, Chen Dong, Gun Zhenqi; Comparison of Lead Tolerance and Enrichment Characteristics of Three Gramineae Plants [J], Journal of Guizhou Normal University (Natural Sciences), 2019, 37(06): 29-33+46.

[0026]

[20] Gao Han, Wang Linna, Huang Fei, Li Peilian, Deng Jingheng. Study on the Enrichment of Cyperus rotundus L. to Zinc [J]. Guangdong Chemical Industry, 2022, 49(12): 40-42.

[0027]

[21] Wang Chao, Bi Jun, Song Xilong, You Haizhou. Tolerance and Enrichment Ability of Six Plants to Zinc [J]. Environmental Science & Technology, 2014, 37(S2): 62-65+200.

[0028]

[22] Tang Yetao, Wu Yudu, Qiu Rongliang, Zeng Xiaowen, Hu Pengjie. Absorption and Enrichment Characteristics of Picris divaricata Vant. to Zinc [J]. Acta Ecologica Sinica, 2009, 29(04): 1823-1831. Summary of the Invention

[0029] The object of the present invention is to provide a method for repairing heavy metal-polluted soil by a plant co-planting mode with a large cumulative amount of six heavy metals, namely Cu, Zn, Pb, Cd, Cr, and Ni, so as to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0030] To achieve the above object, the present invention adopts the following technical solutions.

[0031] A method for phytoremediation of heavy metal contaminated soil by combined planting, which selects shrubs and herbaceous plants tolerant to heavy metals and constructs a plant landscape community on soil contaminated with heavy metals such as Cu, Zn, Cd, Pb, Cr, and Ni. The shrubs and herbaceous plants are Schefflera odorata var. variegata: Ruellia brittoniana: Nerium oleander: Pennisetum alopecuroides.

[0032] More preferably, there are at least 2 other plants spaced between adjacent Nerium oleander plants. Because the crown width of Nerium oleander is relatively large, such an arrangement is conducive to the uniform distribution of its growth space.

[0033] More preferably, Schefflera odorata var. variegata: Ruellia brittoniana: Nerium oleander: Pennisetum alopecuroides are mixed and planted in a ratio of 1 - 2:3 - 5:1 - 2:3 - 5.

[0034] More preferably, when the soil is severely contaminated with Cu, Zn, Pb, and Ni, the planting ratios of Ruellia brittoniana and Pennisetum alopecuroides are increased; when the soil is severely contaminated with Cd, the planting ratio of Pennisetum alopecuroides is increased; when the soil is severely contaminated with Cr, the planting ratios of Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides are increased.

[0035] More preferably, before planting, Schefflera odorata var. variegata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides are divided into seedlings and bagged according to the ratio, and each bag of seedlings is planted in a randomly mixed way.

[0036] As another aspect of the present invention, there is also provided the application of the method for phytoremediation of heavy metal contaminated soil by combined planting as described above in green spaces around industrial areas, wastelands, river floodplains, drawdown zones, and other severely heavy metal - contaminated areas where it is not suitable to plant arbors.

[0037] More preferably, the application includes pruning and harvesting treatments. According to the growth conditions of Schefflera odorata var. variegata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides, pruning is carried out to construct the landscape and harvesting is done, and when harvesting, 5 - 10 cm of the above - ground part is reserved.

[0038] More preferably, Ruellia brittoniana and Pennisetum alopecuroides are harvested 2 - 3 times a year, and Schefflera odorata var. variegata and Nerium oleander are harvested 1 time a year.

[0039] More preferably, the above - ground parts obtained by pruning and harvesting are centrally landfilled, incinerated and ash - formed, and then landfilled as solid waste or used for resource utilization.

[0040] The present invention adopts the above - mentioned technical solutions and has at least the following beneficial effects.

[0041] The present invention selects shrubs and herbaceous plants with relatively fast growth rates and that can be repeatedly harvested, adopts a plant configuration mode of "shrub + herbaceous", and utilizes the characteristics of rapid growth of shrubs and herbaceous plants to solve the problem of slow existing phytoremediation. According to the different root depths of shrubs and herbaceous plants, it can take into account the remediation of heavy metal-contaminated soils in different soil layers. In particular, the combination of multiple plants can remediate soils contaminated with multiple heavy metals. Regular harvesting of fast-growing herbaceous plants can solve the problem of heavy metal release after plant adsorption saturation. Along with the regrowth of plants, heavy metals in the soil can be repeatedly absorbed, and the combination of "shrub and herb" plants creates a layered ground landscape, enhancing the phytoremediation efficiency while also adding landscape effects.

[0042] In the mode of the present invention, the characteristics of deep root systems of shrubs such as Schefflera odorata var. albo-marginata and Nerium oleander can be used to remediate heavy metal-contaminated soils in deeper soil layers, and the characteristics of shallow root systems of Pennisetum alopecuroides and Ruellia brittoniana can be used to remediate surface contaminated soils; after planting, by slightly pruning the shrubs and appropriately pruning the herbs, a better landscape effect can be formed; regular harvesting of fast-growing shrubs and herbs such as Schefflera odorata var. albo-marginata, Pennisetum alopecuroides, and Ruellia brittoniana can achieve the effect of repeated adsorption.

[0043] A method for phytoremediating heavy metal-contaminated soils by combined planting of plants provided by the present invention can be widely used for the remediation of soils in green spaces around industrial areas, abandoned lands, river floodplains, drawdown zones, and other heavy metal seriously contaminated areas where it is not suitable to plant arbors. Specific Embodiments

[0044] To facilitate better understanding of the essence of the present invention by those of ordinary skill in the art, the specific embodiments of the present invention will be elaborated in detail below.

[0045] In the present invention, the tests of each embodiment are field tests, and the test site is located in Xiaolang Village, Luocun Town. The growth conditions of plants and the accumulation of heavy metals by plants under eight configuration modes of planting were studied. The plant configuration modes and the proportions of plants in each mode are as follows.

[0046] Example 1: Random mixing of Schefflera odorata var. albo-marginata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides, with a seedling ratio of 1:4:1:4.

[0047] Example 2: Random mixing of Schefflera odorata var. albo-marginata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides, with a seedling ratio of 2:5:1:3.

[0048] Example 3: Random mixing of Schefflera odorata var. albo-marginata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides, with a seedling ratio of 1:3:2:5.

[0049] Example 4: Random mixing of Schefflera odorata var. albo-marginata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides, with a seedling ratio of 1:3:1:5.

[0050] Control Example 1: Schefflera odorata var. variegata, Ruellia brittoniana, Nerium oleander were randomly mixed, and the ratio of the number of seedlings was 1:4:1.

[0051] Control Example 2: Schefflera odorata var. variegata, Ruellia brittoniana, Pennisetum alopecuroides were randomly mixed, and the ratio of the number of seedlings was 2:5:1.

[0052] Control Example 3: Ruellia brittoniana, Nerium oleander, Pennisetum alopecuroides were randomly mixed, and the ratio of the number of seedlings was 3:2:5.

[0053] Control Example 4: Schefflera odorata var. variegata, Nerium oleander, Pennisetum alopecuroides were randomly mixed, and the ratio of the number of seedlings was 1:1:5.

[0054] For each of the eight configuration modes, 200 m 2 was planted, with 3 replicates, and a total of 600 m 2 was planted for each mode. The plant spacing of the seedlings was 35×35 cm, and they were planted in a random mixing manner according to the proportion of plants in each mode. The soil background data for each mode are shown in Table 1. Regularly observe and record the growth of the plants, and harvest them regularly according to the living habits of the plants. For woody plants, harvest the above-ground parts every six months, and calculate the heavy metal adsorption amount of the plants under repeated harvesting conditions.

[0055] Table 1. Basic soil data

[0056] .

[0057] Sample collection.

[0058] Regularly harvest the above-ground parts of the plants according to their living habits, blanch at 105 °C for 30 min, and dry at 80 °C to constant weight. After drying and grinding the plant samples, pass them through a 0.2 mm sieve for standby.

[0059] Data determination and comparison.

[0060] 1. Growth data determination. Observe and record the growth status of the plants under different plant configuration modes, and regularly measure the plant height of the plants using the direct reading method.

[0061] 2. Heavy metal content determination. After grinding the dried samples, determine the contents of Cu, Zn, Cd, Pb, Cr, and Ni in the above-ground parts. According to the agricultural industry standard method NY / T 1613-2008, after digesting the plant samples with HNO3 - HClO4, use flame atomic absorption spectrophotometry to determine the contents of 6 heavy metal elements.

[0062] 3. Single-plant heavy metal accumulation. According to the heavy metal contents in the above-ground parts of the plants in different "shrub, herb" configuration modes, calculate the single-plant accumulation amounts of the six heavy metals in the above-ground parts of the plants in each mode.

[0063] 4. Heavy metal accumulation per mu. Based on the heavy metal contents in the above-ground parts of plants in different "irrigation, grass" configuration modes, combined with the proportions of plants in each configuration mode, calculate the above-ground parts of plants in each mode's accumulation of 6 heavy metals per mu.

[0064] Table 2. Growth conditions of plants planted for 1 year in different modes

[0065] 。

[0066] As can be seen from Table 2, in the case of combined planting of four plants, the comprehensive growth effect is the best; especially the growth of Ruellia brittoniana is the best. Thus, it can be seen that the combined planting of four plants can play a role in promoting each other's growth.

[0067] Table 3. Single-plant accumulation of heavy metals by plants under different configuration modes

[0068] 。

[0069] As can be seen from Table 3, for the configuration modes of each embodiment of the present invention, the accumulation amounts of Cu, Zn, Cd, Pb, Cr, and Ni are significantly greater than those of the comparative examples. The combined planting of four plants can promote the heavy metal accumulation amount of a single plant.

[0070] Table 4. Above-ground heavy metal accumulation per mu under different configuration modes after half a year of planting

[0071] 。

[0072] As can be seen from Table 4, the four-plant combined planting modes provided in Embodiments 1-4 of the present invention can significantly improve the accumulation of Cu, Zn, Cd, Pb, Cr, and Ni in the above-ground parts of each plant, indicating that the combined planting of four plants can promote the absorption of heavy metals such as Cu, Zn, Cd, Pb, Cr, and Ni by a single plant.

[0073] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0074] The above embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. The parts not described in the specific embodiments are all prior art or common general knowledge.

[0075] In addition, it should be noted that in the description of the present invention, the detailed description of the preferred implementation methods of the present invention and the included embodiments can more easily understand the content of the present invention. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. When there is a contradiction, the definition in this specification shall prevail.

[0076] In the present invention, the term "prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing" or any other variation thereof used in the present invention are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or device containing the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article or device.

[0077] In the present invention, when an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed individually. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in the present invention, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0078] Furthermore, the indefinite articles "a" and "an" before an element or component of the present invention do not limit the number requirement (i.e., the number of occurrences) of the element or component. Therefore, "a" or "an" should be interpreted to include one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

Claims

1. A method for phytoremediation of heavy metal contaminated soil by combined planting of plants, characterized in that, Select shrubs and herbaceous plants that are tolerant to heavy metals, and construct a plant landscape community on soil polluted by heavy metals such as Cu, Zn, Cd, Pb, Cr, and Ni. The shrubs and herbaceous plants are Schefflera odorata var. variegata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides. Schefflera odorata var. variegata: Ruellia brittoniana: Nerium oleander: Pennisetum alopecuroides are mixed and planted in a ratio of 1-2:3-5:1-2:3-5, and there is at least a 2-plant interval of other plants between adjacent Nerium oleander plants.

2. The method for phytoremediation of heavy metal contaminated soil by combined planting of plants according to claim 1, characterized in that, When the soil is severely polluted by Cu, Zn, Pb, and Ni, increase the planting ratios of Ruellia brittoniana and Pennisetum alopecuroides. When the soil is severely polluted by Cd, increase the planting ratio of Pennisetum alopecuroides. When the soil is severely polluted by Cr, increase the planting ratios of Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides.

3. A method for phytoremediation of heavy metal contaminated soil by combined planting of plants according to claim 1, characterized in that, Before planting, divide the seedlings of Schefflera odorata var. variegata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides into bags according to the ratio, and plant each bag of seedlings in a randomly mixed way.

4. Application of a method for phytoremediation of heavy metal-polluted soil by combined planting of plants as described in any one of claims 1-3 in a severely heavy metal-polluted area where it is not suitable to plant trees.

5. The application according to claim 4, characterized in that Severely heavy metal-polluted areas where it is not suitable to plant trees include green spaces around industrial areas, abandoned lands, river floodplains, and drawdown zones.

6. The application according to claim 4, characterized in that, It includes pruning and harvesting treatments. Prune and construct the landscape according to the growth conditions of Schefflera odorata var. variegata, Ruellia brittoniana, Nerium oleander, and Pennisetum alopecuroides, and harvest. When harvesting, leave 5-10 cm of the above-ground part.

7. The application according to claim 6, wherein Ruellia brittoniana and Pennisetum alopecuroides are harvested 2-3 times a year, and Schefflera odorata var. variegata and Nerium oleander are harvested once a year.

8. The application according to claim 6, wherein The above-ground parts obtained by pruning and harvesting are centrally landfilled, incinerated and ash-treated, and then landfilled as solid waste or utilized resourcefully.